Numerical simulation of aerodynamic noise for the two-stage adjustable-blade axial-flow fan

Abstract

In this paper, a three-dimensional calculation model of a two-stage adjustable-blade axial-flow fan is established and verified by grid independence and numerical accuracy. The pressure distribution and sound power-level distribution characteristics of the blade surface are explored with variable blade installation angles. Based on the Q-criterion, the study reveals the spatial distribution of the channel and trailing-edge shedding and channel vortexes in the flow field. Then, the evolution laws of the fan's aerodynamic noise sound pressure level are also investigated, and its frequency domain characteristics with variable blade installation angles are obtained. The results show that when the rotor blade installation angle is −5°, the front-guide vane matches the installation angle of the first-stage impeller. The upper limit of sound power level is the smallest with variable blade installation angles, which is 123.56 dB. Meanwhile, the number and size of vortex structures in the front-guide vane area are the smallest, and the turbulent flow in the flow field is moderate. As the moving blade installation angle is deflected from −10° to 10°, the total sound pressure level of aerodynamic noise at each component of the fan first decreases and then increases. The minimum value is 121.40 and 128.40 dB at the inlet and outlet when the blade installation angle is −5°. In addition, the number of eddies periodically shed in the fan flow field is the least. This research can supply technical support for the noise reduction of the two-stage adjustable blade axial fan.